Solar heat exchanger controller

ABSTRACT

A circuit board controller enables a solar hot water system to be used in conjunction with, and assist, a conventional heating system such as a furnace. If some heat is available from solar heating, then the solar heat is used for pre-heating so the conventional heating system does not have to perform as much work. If there is enough heat available from solar heating to provide all of the heat that is needed, then operation of the conventional heating system is locked out.

RELATED APPLICATION

This application is a continuation-in-part of U.S. patent application Ser. No. 12/545,801, entitled “Solar Heat Exchanger”, and filed Aug. 21, 2009, which is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to systems for the collection, storage and transfer of heat energy and, more particularly, to heat pump systems.

SUMMARY OF THE INVENTION

The present invention is directed to a solar heat exchanger for assisting an air-to-air heat pump system. An air-to-air heat pump loses its ability to produce heat when the ambient temperature is low. The solar heat exchanger of the invention enables warm solar solution to be introduced into thermal contact with the saturated vapor. This may allow the refrigerant to extract more heat at low ambient temperatures, so an air-to-air heat pump will be able to produce its designed heating ability at lower temperatures. The solar heat exchanger may run simultaneously and in parallel with the heat pump to thereby improve the efficiency of the heat pump.

In an air-to-air heat pump system, when the ambient temperature is low, the system does not extract or produce the amount of heat that the system is capable of. Thus, in cold weather there may need to be backup heat, such as electric strip heat, or else the heat pump is locked out and the furnace is turned on. The present invention may introduce solar warmed water into the air-to-air heat pump. A heat exchanger is provided which may be thought of as a tube within a tube. The refrigerant may flow through the inside of the internal tube, and the warm solar water may flow through the external tube. Thus, the invention may introduce the warmed solar water into thermal contact with the refrigerant which has not reached full potential with regard to the amount of heat the refrigerant can extract from the air. The warm water may introduce heat into the refrigerant, and the heat may then be transferred to a condenser coil inside a building in which the heat pump is installed. Inside the building, the heat is introduced into the air and raises the air temperature within the building.

In one particular embodiment, a circuit board controller enables a solar hot water system to be used in conjunction with, and assist, a conventional heating system such as a furnace. If some heat is available from solar heating, then the solar heat is used for pre-heating so the conventional heating system does not have to perform as much work. If there is enough heat available from solar heating to provide all of the heat that is needed, then operation of the conventional heating system is locked out.

In another particular embodiment, the invention includes a solar heating arrangement for use in conjunction with a conventional heating system having a thermostat. The arrangement includes a solar heating system and an electronic controller electrically connected to the thermostat of the conventional heating system and to the solar heating system. The electronic controller locks out the conventional heating system and use heat only from the solar heating system if a liquid from the solar heating system is above a threshold temperature set by the thermostat. The electronic controller supplements heat from the conventional heating system with heat from the solar heating system if the liquid from the solar heating system is below the threshold temperature set by the thermostat but is warmer than a fluid to be heated by the conventional heating system. The electronic controller locks out the solar heating system if the liquid from the solar heating system is below the threshold temperature set by the thermostat and is cooler than a fluid to be heated by the conventional heating system.

In yet another particular embodiment, the invention includes a heating arrangement having a furnace and solar relay coil interconnecting a yellow terminal of a thermostat and a yellow terminal of a furnace. The furnace and solar relay coil are magnetically coupled to a furnace relay. A parallel combination of the furnace relay and a heat pump relay is connected in a first series combination with an isolation relay, a first temperature switch, and a zone valve coil. The first temperature switch senses a temperature of a liquid associated with a solar heating system. A first fixed voltage is applied across the first series combination. The heat pump relay is magnetically coupled to a heat pump and solar relay coil. The heat pump and solar relay coil interconnects the yellow terminal of the thermostat and the common terminal of the furnace. The zone valve coil is magnetically coupled to an end switch relay. The end switch relay being connected in a second series combination with a circulator pump coil. A second fixed voltage is applied across the second series combination. The circulator pump coil is magnetically coupled to a circulating pump relay. The circulating pump relay is connected in a third series combination with a circulating pump motor. A third fixed voltage is applied across the third series combination. The circulating pump motor circulates the liquid from the solar heating system. An isolation relay coil is magnetically coupled to the isolation relay. The isolation relay coil interconnects an orange terminal of the thermostat and the common terminal of the furnace. A fourth fixed voltage is applied across a fourth series combination including a second temperature switch and a furnace heat pump relay coil. A furnace lockout relay is magnetically coupled to the furnace heat pump relay coil and interconnects a white terminal of the thermostat and a white terminal of the furnace. A heat pump lockout rely is magnetically coupled to the furnace heat pump relay coil and interconnects the yellow terminal of the thermostat and the yellow terminal of the furnace.

An advantage of the invention is that it enables a heat pump to heat a building adequately at low outside temperatures.

Another advantage is that the invention may use the free heat provided by solar panels to increase the efficiency of a heat pump.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of the invention will become more apparent to one with skill in the art upon examination of the following figures and detailed description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views.

FIG. 1 is a block diagram of one embodiment of an air-to-air heat pump system of the present invention including a solar heat exchanger.

FIG. 2 a is a diagram of the heat exchanger of FIG. 1.

FIG. 2 b is a partially sectional diagram of the heat exchanger of FIG. 1.

FIG. 3 is a block diagram of another embodiment of an air-to-air heat pump system of the present invention including a solar heat exchanger.

FIG. 4 is a block diagram of one embodiment of a forced air system of the present invention including a solar heat exchanger.

FIG. 5 is a schematic diagram of one embodiment of a circuit board controller of the present invention.

FIG. 6 is another schematic diagram of the circuit board controller of FIG. 5.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Referring to FIG. 1, there is shown one embodiment of the air-to-air heat pump system 10 of the present invention. System 10 includes an indoor coil 12 and an outdoor coil 14. Refrigerant circulates, as indicated by arrows 16 in a closed circuit including coils 12, 14 and conduits 18, 20. System 10 also includes a thermal expansion valve 22 for heating with internal bypass, and a thermal expansion valve 24 for cooling with internal bypass.

A reversing valve 25 reverses the flow of refrigerant through the circuit depending on whether system 10 is operating in a heating mode or a cooling mode. With a counterclockwise circulation, as indicated by arrows 16, system 10 operates in a heating mode (i.e., heats the indoor side of the circuit). Conversely, with a clockwise circulation, system 10 operates in a cooling mode. System 10 further includes a filter drier 26 and an accumulator 28.

According to the invention, a solar heat exchanger 30 is in contact with, and may encircle or surround conduit 20. Both exchanger 30 and conduit 20 may be formed of a thermally conductive material, such as copper, for example. Exchanger 30 may be donut-shaped or circular in cross section and substantially hollow. Exchanger 30 may have a fluid input 32 and a fluid output 34. Both input 32 and output 34 may be in fluid communication with solar heater 36. Solar heater 36 may heat water, propylene glycol, or some other heat transfer fluid and pump the water in the direction indicated by arrow 38 into exchanger 30.

While in exchanger 30, the heat in the water from heater 36 may be transferred to the saturated refrigerant in conduit 20. Such heat transfer may assist in heating indoor coil 12 and improve the efficiency of system 10. After passing through heat exchanger 30, the water exits through outlet 34 and returns to heater 36 where the water is re-heated and the cycle repeats.

According to the invention, when the water from heater 36 is hot enough, the heating operation of the air-to-air heat pump may be locked out such that all the heat produced by the system is produced exclusively by solar heater 36. Conversely, when system 10 operates in the cooling mode, solar heater 36 may be locked out such that the refrigerant is not heated further when passing through exchanger 30.

FIG. 2 a illustrates exchanger 30 including input 32 and output 34. FIG. 2 b further illustrates a sectional view of a central portion of exchanger 30. As shown, conduit 20 extends through exchanger 30. As also shown, the direction of refrigerant flow in conduit 20 may be opposite to the direction of water flow in exchanger 30. Heat exchanger 30 may be generally located between outside coil 14 and a liquid receiver including filter drier 26 and accumulator 28.

In one embodiment, heat exchanger 30 has a length 40 (FIG. 2 a) of approximately between twelve and fifteen inches. However, there may be no limit to the length of exchanger 30, and it may be up to about three feet long. Advantageously, the greater the length 40 of exchanger 30, the more completely it may transfer its heat to conduit 20.

In one embodiment, an inner cylindrical wall 42 of exchanger 30 is concentric with an outer cylindrical wall 44 of exchanger 30. Thus, exchanger 30 may have a donut-shaped cross section. However, in another embodiment, exchanger 30 has no inner wall 42 (or inner wall 42 may be thought of as being at least a part of conduit 20), and its opposite ends 46 are sealed fluid-tight against the outer surface of conduit 20. Thus, the heat transfer fluid with exchanger 30 directly contacts the outer surface of conduit 20. Thus, exchanger 30 may have a circular cross section. In both of these embodiments, the only path by which the heat transfer fluid may exit exchanger 30 may be through output 34.

FIG. 3 illustrates another embodiment of an air-to-air heat pump system 300 of the present invention. Heat from the solar water is used to heat the air coil first to get as much heat as possible in the conditioned air stream. The cooler water is then used to put heat in the heat pump refrigerant. System 300 includes a solar collector 302, such as a solar panel, that heats water, propylene glycol, or some other liquid and send the heated liquid in conduit 304 to a solar heat storage tank 306. After the heat in the liquid has been transferred to tank 306, a conduit 308 carries the liquid back to collector 302 for re-heating. A pump (not shown) may be used between solar collector 302 and tank 306 to create the circulation of liquid. In one embodiment, tank 306 may be as described in patent application Ser. No. 12/536,409, entitled Heat Storage and Transfer System, filed Aug. 5, 2009, which is hereby incorporated by reference in its entirety.

Within tank 306, the heat from collector 302 may be transferred to another liquid such as water or propylene glycol that circulates between tank 306, heat exchanger 310, and water coil 312. Conduit 314 carries hot liquid to heat exchanger 310 and water coil 312. The heat in the liquid is transferred to heat exchanger 310 and water coil 312, and is returned to tank 306 for re-heating via conduit 316.

Heat exchanger 310 may be incorporated in an air-to-air heat pump 318 such that heat exchanger 310 assists in the heating of the heat pump's refrigerant, such as described above with regard to FIG. 1. Heat pump 318 may be substantially similar to the heat pump described with regard to FIG. 1. Thus, the warm solar water may deliver heat to heat pump 318 so heat pump 318 can deliver full capacity heat when the ambient temperature is low.

FIG. 4 illustrates one embodiment of a forced air heat system 400 of the present invention that marries solar hot water heat to a forced air system. System 400 includes a solar collector 402, such as a solar panel, that heats water, propylene glycol, or some other liquid and sends the heated liquid in conduit 404 to a solar heat storage tank 406. After the heat in the liquid has been transferred to tank 406, a conduit 408 carries the liquid back to collector 402 for re-heating. Conduits 404, 408 may be fluidly connected within tank 406 such that conduits 404, 408 conjunctively form a single, unitary conduit or coil within tank 406. A pump (not shown) may be used between solar collector 402 and tank 406 to create the circulation of liquid. In one embodiment, tank 406 may be as described in patent application Ser. No. 12/536,409, entitled Heat Storage and Transfer System, filed Aug. 5, 2009, which is hereby incorporated by reference in its entirety.

A valve controller 410 may control valves 412, 414 which may divert the heated liquid from solar collector 402 to a heat dissipater 416 where the heat may be used immediately for heating water or air, for example. To the extent that the need for immediate heat is satisfied, heat may alternatively diverted by controller 410 to storage tank 406.

Within tank 406, the heat from collector 402 may be transferred to another liquid such as water that circulates between tank 406, water heater 418, and hot water coil 420. Conduit 422 carries hot liquid to water heater 418 and hot water coil 420. The water in water heater 418 may be further heated in water heater 418 and released for use via conduit 426. The water expelled through conduit 426 may be replenished via a cold water supply conduit 428.

The heat in the water in conduit 422 may be transferred to hot water air coil 420 where the heat may be transferred to air in a return air duct of a forced air system. After passing through hot water coil 420, the water is returned to tank 406 for re-heating via conduit 424. Conduit 424 also receives cold water from the cold water supply via conduit 428.

A check valve 430 and a shutoff valve 432 may be provided between conduit 422 and the cold water inlet of water heater 418. A bypass shut off valve 434 may be provided between conduit 428 and the cold water inlet of water heater 418. Thus, the cold water inlet of water heater 418 may be selectively in fluid communication with conduit 422 and/or with cold water source 428.

A shutoff valve 436 and a check valve 438 may be provided between conduit 428 and cold water inlet 424 of storage tank 406. A circulation pump 440 and a zone valve 442 may be provided between conduit 422 and the hot water inlet of hot water coil 420. Pump 440 may circulate water between hot water coil 420 and conduit 422.

As described above, the cold water inlet of the water heater may be selectively in fluid communication with a source of cold water 428, and the conduit 424 may be selectively in fluid communication with the source of cold water 428. Conduits 422 and 424 may be in fluid communication with each other within tank 406, and thus may be referred to herein as being a single, unitary conduit. This unitary conduit conjunctively formed by conduits 422, 424 may be in the form of a coil within tank 406. In one embodiment, this coil is disposed radially outwardly from the coil formed by conduits 404, 408. Hot water coil 420 of the forced air heating system may be in selective fluid communication with the conduit that is conjunctively formed by conduits 422 and 424.

Temperature switches 444, 446 may control the egress of hot water from tank 406 via conduit 422 and the ingress of cold water into tank 406 via conduit 424, respectively. Switches 444, 446 may be disposed underneath a layer of insulation on the outside of tank 406.

In another embodiment, the invention includes a circuit board that enables a solar hot water system to operate in conjunction with any heating system, such as a heating system including a boiler and/or a forced air heat pump. Thus, the circuit board of the invention enables a solar hot water system to run simultaneously with a conventional heat system.

In one embodiment, the circuit board can lock out the conventional heat system and let the solar system run exclusively when the water is hot enough. The circuit board may also include a safety feature that locks out the solar-based system when air conditioning is running.

The circuit board may tie solar heating in with conventional type forced air heating systems. A forced air heating system usually includes a furnace having a blower package in it. An outside unit may include an air conditioning unit or a heat pump. The thermostat may control the staging of heat and the staging of cooling. Whenever heating is desired, the first state usually brings on the heat pump. The heat pump may operate and try to satisfy the thermostat setting point. However, if the heat pump is not able to increase the temperature to the thermostat setting point, then the furnace kicks on and provides the heat needed to heat the house up to the desired temperature.

In cooling, the reversing valve may be energized, and, assuming that the outdoor unit is a heat pump, then the cooling may start. The energization of the reversing valve may reverse the refrigerant flow from the heating mode. In this scenario, the outdoor unit may become a condenser that extracts the heat from the house. This operation may continue until the thermostat is satisfied and the unit is shut down. The only ties the outdoor unit may have with the furnace may be through the low voltage control wiring and in controlling the blower to distribute the air throughout the house.

The solar system may be a totally independent system by itself. However, the circuit board of the present invention may enable adapting the solar system to any conventional heating system. This enabling may be provided by relays which may turn on or turn off the solar system depending upon whether heat is available and may also turn on the heat pump or the furnace according to whichever is needed at the time. There may be a certain temperature set point on the thermostat in the header and as long as the water temperature is above that set point then the circulator pump may circulate the hot water to the solar storage tank. When heating is desired, if this water temperature is up to a certain set point then the circulator pump may circulate the water to a water coil that is installed in the duct work. At the same time, the blower may be turned on. If the water is not hot enough to do the total heating on its own, then a backup system, which could be either the heat pump or the furnace, could kick on with the hot water-based heating. The solar heating unit could preheat the air and this would cut down on the operation time of the furnace or the heat pump. If the water is above a second set point temperature, then the solar heating unit could heat the air totally by itself. At this time, the furnace or heat pump could be locked out of operation. The blower could be energized so that the blower is running with the solar circulating pump, and hot water is circulating between the solar storage tank and the water coil. The blower could continue to run until the thermostat is satisfied, and then the whole system could be shut down.

Whenever air conditioning is desired, the solar heating unit could be de-energized because it would not be desirable for hot water to circulate to the coil. Thus, a lock out relay may totally lock out the solar heating unit and/or the heat pump at the time of air conditioning. The circuit board of the invention may be able to not only make a solar system work with the conventional heating system, but may also be able to utilize all the heat that can be gathered during sunny time periods or even on partially cloudy days. The solar heating system may perform not only total heating of the house, but may also raise the temperature of the air before the air gets to the furnace or to the heat pump so that a quicker satisfaction of the thermostat can be made. This may even shorten the time duration that a home owner would be using electricity or gas to heat their home. During time periods in which enough heat is collected by the solar unit, then the solar unit could do all the heating of the house, and no electricity or gas may be used. Thus, the circuit board of the invention may be able to adapt a solar heating unit to almost any conventional heating system.

Now, with reference to FIGS. 5 and 6, will be described a sequence of operations for the circuit board controls that may marry solar heating with any conventional heating system. The thermostat may be for a system with five wires. The wire terminations may be designated as follows:

R—This wire comes from the 24VAC transformer on the heating system. C—This wire comes from the 24VAC transformer on the air-conditioning system. W—This wire comes from the relay that turns on the heating system. Y—This wire comes from the relay that turns on the cooling system. G—This wire comes from the relay that turns on the fan. These designations may be further described as follows:

{Terminal Name}, {Color}, {Function}:

-   -   (R), Red, hot side of transformer.     -   (C) Common side of transformer     -   (Y), Yellow, Compressor activity (cooling or cooling and heating         on a heat pump).     -   (W) White, “Heat” (gas burner, oil burner, electric heat,         (auxiliary heat on a heat pump including defrost output from the         outdoor unit to activate electric heat and turn on the AUX. heat         lamp).     -   (G), Green, furnace blower fan. (needed for air conditioning,         heat pumps and some electric furnaces).     -   (O), Orange, Energize to cool (used for reversing valve on heat         pumps)

In one embodiment, terminal Y calls for heat by becoming energized. As a result of voltage being applied at terminal Y, the heat pump lock out relay 502 is closed. A voltage signal is applied to the heat pump and starts the heating mode. The heat pump and solar relay coil 504 is energized and thereby the heat pump and solar relay 505 is closed. If water temperature switch 1 (506) is satisfied from the water being warm enough, then it may energize the zone valve coil 508, thereby opening the water gate and closing the end switch relay 510, energizing circulator pump relay coil 512, closing circulator pump relay 514 and energizing the circulator pump 516 to circulate the water to the water coil.

Terminal W may call for heat by becoming energized. As a result of voltage being applied at terminal W, the furnace lock out relay 518 is closed, and a voltage signal is applied to the furnace and starts the heat mode. Terminal W also applies voltage to the normally open fan relay 520. Terminal W's call for heat may also energize the furnace and solar coil 522.

Voltage may be applied to the normally closed isolation relay 524, and the furnace and solar relay 526 may be closed. If water temperature switch 1 (506) is made closed, then zone valve coil 508 may be energized, thereby opening the water gate. End switch relay 510 may close, energizing circulator pump coil 512, closing circulator pump relay 514, and energizing circulator pump 516. This may also circulate warm water within the furnace and help to offset the air temperature so that the furnace does not have to work as hard or heat as long.

Temperature switch 2 (528) may then close, and the water may be hot enough to do the heating. The furnace and heat pump lock out relay coil 530 is energized, thereby opening the heat pump lock out relay 502 and the furnace lock out relay 518 and closing the fan relay 520. This function may enable the solar water to circulate through the furnace and the heat pump may be locked out. The fan may run to circulate the warm air through the house. In this mode the solar heating may be doing most or all of the heating in the house.

When terminal O is energized for cooling, the isolation relay coil 532 is energized, thereby opening the isolation relay 524. This may de-energize the solar controls because it is not desirable for the solar heat to be working when the environment is being cooled. Physically adjacent to isolation relay 524 may be cooling relay 525, as shown in FIG. 6.

A novel feature of the controller illustrated in FIGS. 5 and 6 is that it marries a solar heating system with a conventional heating system. Another novel feature of the present invention is the way the water coil is installed in the system, which is on the return air side. The air can be going across as long as the water temperature is above the ambient temperature in the room, or above the desired temperature, and if the air temperature can offset or warm the air temperature going across the water coil. This may also allow the heat pump or the furnace to not have to work as hard or run as long, and so the solar heat is being taken advantage of as much as possible. When the solar tank is at the right temperature, then the furnace and the heat pump can be isolated all together just circulating warm water, which is a solar hydraulic heating system.

The controller of FIGS. 5 and 6 may be used to many a solar hot water system with a geothermal system, a heat pump or a furnace system. The controller may lock out the heat pump or furnace or lock out the geothermal system whenever the water is hot enough to do the heating on its own. Also, the system may circulate the warm water working with the geothermal or working with the heat pump and furnace. By doing this, the air temperature can be offset and the systems do not have to work as hard.

While the present invention has been described with reference to specific exemplary embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention as set forth in the claims. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. 

1. A solar heating arrangement for use in conjunction with a conventional heating system having a thermostat, the arrangement comprising: a solar heating system; and an electronic controller electrically connected to the thermostat of the conventional heating system and to the solar heating system, the electronic controller being configured to: lock out the conventional heating system and use heat only from the solar heating system if a liquid from the solar heating system is above a threshold temperature set by the thermostat; supplement heat from the conventional heating system with heat from the solar heating system if the liquid from the solar heating system is below the threshold temperature set by the thermostat but is warmer than a fluid to be heated by the conventional heating system; and lock out the solar heating system if the liquid from the solar heating system is below the threshold temperature set by the thermostat and is cooler than a fluid to be heated by the conventional heating system.
 2. An arrangement as in claim 1 in which the electronic controller interconnects terminals of a thermostat with terminals of a furnace.
 3. An arrangement as in claim 1 in which the electronic controller is configured to use heat from the solar heating system by turning on a circulating pump that circulates a heated fluid through coils in an air duct.
 4. An arrangement as in claim 3 in which the electronic controller includes a temperature switch configured to energize a zone valve coil, the zone valve coil being configured to open and close an end switch relay, the end switch relay being configured to energize a circulator pump coil for closing a circulating pump relay for applying voltage to the circulating pump.
 5. An arrangement as in claim 1 in which the electronic controller includes a temperature switch configured to energize a furnace heat pump relay coil, the furnace heat pump relay coil being configured to open and close a furnace lockout relay and/or a heat pump lockout relay for locking out the conventional heating system.
 6. An arrangement as in claim 5 in which the furnace heat pump relay coil is configured to open and close a furnace lockout relay that interconnects a white terminal of a thermostat and a white terminal of a furnace.
 7. An arrangement as in claim 5 in which the furnace heat pump relay coil is configured to open and close a heat pump lockout relay that interconnects a yellow terminal of a thermostat and a yellow terminal of a furnace.
 8. A heating arrangement comprising: a furnace and solar relay coil interconnecting a yellow terminal of a thermostat and a yellow terminal of a furnace, the furnace and solar relay coil being magnetically coupled to a furnace relay, a parallel combination of the furnace relay and a heat pump relay being connected in a first series combination with: an isolation relay; a first temperature switch; and a zone valve coil, the first temperature switch being configured to sense a temperature of a liquid associated with a solar heating system, a first fixed voltage being applied across the first series combination, wherein the heat pump relay is magnetically coupled to a heat pump and solar relay coil, the heat pump and solar relay coil interconnecting the yellow terminal of the thermostat and the common terminal of the furnace, the zone valve coil is magnetically coupled to an end switch relay, the end switch relay being connected in a second series combination with a circulator pump coil, a second fixed voltage being applied across the second series combination, the circulator pump coil being magnetically coupled to a circulating pump relay, the circulating pump relay being connected in a third series combination with a circulating pump motor, a third fixed voltage being applied across the third series combination, the circulating pump motor being configured to circulate the liquid from the solar heating system, an isolation relay coil being magnetically coupled to the isolation relay, the isolation relay coil interconnecting an orange terminal of the thermostat and the common terminal of the furnace, a fourth fixed voltage being applied across a fourth series combination including a second temperature switch and a furnace heat pump relay coil, a furnace lockout relay being magnetically coupled to the furnace heat pump relay coil and interconnecting a white terminal of the thermostat and a white terminal of the furnace, and a heat pump lockout rely being magnetically coupled to the furnace heat pump relay coil and interconnecting the yellow terminal of the thermostat and the yellow terminal of the furnace.
 9. An arrangement as in claim 8 in which the second temperature switch is configured to sense a temperature of the liquid from the solar heating system.
 10. An arrangement as in claim 9 in which the second temperature switch is configured to open or close in response to the liquid being hot enough to perform heating.
 11. An arrangement as in claim 8 in which the first, second and fourth series combinations are connected in parallel, each of the first, second and fourth voltages being a same voltage approximately between eighteen and thirty volts.
 12. An arrangement as in claim 8 further comprising a cooling relay coil interconnecting the white terminal of the thermostat and the common terminal of the furnace.
 13. An arrangement as in claim 8 in which a red terminal of the thermostat is directly connected to a red terminal of the furnace.
 14. A solar heating arrangement for use in conjunction with a conventional heating system having a thermostat, the arrangement comprising: a solar heating system; and an electronic controller electrically connected to the thermostat of the conventional heating system and to the solar heating system, the electronic controller including: means for locking out the conventional heating system and using heat only from the solar heating system if a liquid from the solar heating system is above a threshold temperature set by the thermostat; means for supplementing heat from the conventional heating system with heat from the solar heating system if the liquid from the solar heating system is below the threshold temperature set by the thermostat but is warmer than a fluid to be heated by the conventional heating system; and means for locking out the solar heating system if the liquid from the solar heating system is below the threshold temperature set by the thermostat and is cooler than a fluid to be heated by the conventional heating system.
 15. An apparatus as in claim 14 in which the means for locking out the conventional heating system includes means for allowing the liquid from the solar heating system to circulate through a coil.
 16. An apparatus as in claim 14 in which the electronic controller interconnects terminals of a thermostat with terminals of a furnace.
 17. An arrangement as in claim 14 in which the electronic controller includes means for using heat from the solar heating system by turning on a circulating pump that circulates a heated fluid through coils in an air duct.
 18. An arrangement as in claim 14 in which the electronic controller includes a temperature switch configured to energize a furnace heat pump relay coil, the furnace heat pump relay coil being configured to open and close a furnace lockout relay and/or a heat pump lockout relay for locking out the conventional heating system.
 19. An arrangement as in claim 18 in which the furnace heat pump relay coil is configured to open and close a furnace lockout relay that interconnects a white terminal of a thermostat and a white terminal of a furnace.
 20. An arrangement as in claim 18 in which the furnace heat pump relay coil is configured to open and close a heat pump lockout relay that interconnects a yellow terminal of a thermostat and a yellow terminal of a furnace. 